Method of manufacturing semiconductor device and wire bonding apparatus

ABSTRACT

A terminal of a compact wire loop with a great strength of bonding is formed by a method including: a first folding step in which a tip end of a capillary is raised by a height of H 1  from a point  86   a  where the center of the capillary is positioned during second bonding on a lead  74  to a point “p”, and then moved horizontally by a first distance of L 1  toward a pad  73 , and lowered to a point “r”; a second folding step in which the tip end of the capillary is raised from the point “r” to a height of H 2  and then moved horizontally toward the lead  74  by a second distance of L 2 ; and a third bonding step in which the center of the capillary is aligned with and then lowered to a point  87   a  on the lead  74  adjacent to the point  86   a.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing asemiconductor device including a wire loop to be formed by wire bonding,and to a structure of a wire bonding apparatus for use in the method.

2. Description of the Related Art

In semiconductor manufacturing processes, wire bonding apparatuses areoften used for bonding of thin metallic wires to electrode pads on asemiconductor chip and electrode leads on a lead frame for connectiontherebetween. Many wire bonding apparatuses include a bonding armconfigured to be rotated with a drive motor, an ultrasonic horn attachedto the bonding arm, a capillary attached at one end of the ultrasonichorn, and an ultrasonic vibrator attached to the ultrasonic horn. Insuch wire bonding apparatuses, the bonding arm is driven and rotated tomove the capillary in a direction toward and away from a pad or lead andto bond an initial ball formed at a tip end of the capillary or a wireto the pad or lead, and then the ultrasonic horn is resonated with theultrasonic vibrator to provide ultrasonic vibration at the tip end ofthe capillary for bonding.

For wire connection between a pad and a lead using such a wire bondingapparatus, a method is generally employed in which a wire extending outof the tip end of the capillary is first formed into an initial ball andthe initial ball is bonded onto the pad, and then the capillary israised to loop and bond the wire onto the lead, thereafter the wire israised together with the capillary and cut off (see FIGS. 5 and 6 ofJapanese Patent No. 3830485, for example). The method for wireconnection between a pad and a lead provides a sufficient strength ofbonding between the pad and wire because the initial ball is bonded tothe pad. However, the strength of bonding between the lead and wire cannot be sufficient because only a lateral face of the wire is bonded tothe lead.

To address this problem, there has been proposed a method in which aftera wire is bonded to a lead, the capillary is raised toward a pad whilethe wire is fed out, and then the wire is re-bonded at a positionfarther from the pad than the position where first bonded to the lead,thereafter the wire is raised together with the capillary and cut off(see FIG. 2 of Japanese Patent No. 3830485, for example). There has alsobeen proposed a method in which after a wire is bonded to a lead, thecapillary is raised and lowered to be brought into contact with the leadat a position farther from a pad than the position where first bonded tothe lead to apply ultrasonic vibration thereto (see FIG. 4 of JapanesePatent No. 4365851, for example).

However, in the related art described in Japanese Patent No. 3830485,since the wire is bonded to the lead to form a wire loop and then thecapillary is moved while the wire is fed out to form a second small wireloop on the opposite side of the lead with respect to the pad, it isnecessary for stable formation of the second wire loop to increase thewire feed length, so that the wire is likely to be formed into a loopshape. Thus increasing the wire feed length will result in an increasein the size of the second wire loop and thereby require the lead to havean increased area for bonding, suffering from a problem of increase inthe size of the semiconductor device. Also, in the related art describedin Japanese Patent No. 4365851, since the capillary is brought intocontact with the lead at a position farther from a pad than the positionwhere first bonded to the lead, it is necessary for the lead to have anincreased length, suffering from a problem of inadequacy inmanufacturing a compact semiconductor device.

BRIEF SUMMARY OF THE INVENTION

It is hence an object of the present invention to provide a compact wireloop with a great strength of bonding.

The present invention is directed to a method of manufacturing asemiconductor device having a wire loop connecting a first bonding pointand a second bonding point using a wire bonding apparatus having a loadsensor for detecting pressing load applied at a tip end of a capillary,the method including: a first bonding step; a second bonding step; afirst folding step; a second folding step; a third bonding step; thefirst bonding step of bonding a wire fed out of a tip end of a capillaryto a first bonding point by means of the capillary; the second bondingstep of, after completing the first bonding step, bonding the wire to asecond bonding point by means of the capillary in such a manner that thecapillary is raised while feeding the wire out of the tip end thereofand subsequently looped toward the second bonding point along apredetermined trajectory and subsequently lowered to bond the secondbonding point with a face portion located at the first bonding pointside of the capillary, thereby forming a wire loop between the firstbonding point and the second bonding point; the first folding step of,after completing the second bonding step, folding the wire to the wireloop by means of the capillary in such a manner that the capillary israised in a substantially vertical direction while feeding the wire outof the tip end thereof and subsequently moved in a substantiallyhorizontal direction and toward the first bonding point by a firstpredetermined distance, and then the capillary is lowered in asubstantially vertical direction and to the wire loop until the pressingload detected with the load sensor becomes equal to a predeterminedvalue, thereby forming the wire fed out of the tip end of the capillaryinto a first folded portion having a shape that follows the upper faceon the wire loop; the second folding step of, after completing the firstfolding step, folding the wire to the first folded portion by means ofthe capillary in such a manner that the capillary is raised in asubstantially vertical direction while further feeding the wire out ofthe tip end thereof and subsequently moved away from the first bondingpoint by a second predetermined distance, and then the capillary issubstantially lowered in a substantially vertical direction, therebyforming the wire further fed out of the tip end of the capillary into asecond folded portion having a shape that follows the upper face on thefirst folded portion; and the third bonding step of, after completingthe second folding step, bonding the wire by means of the capillary insuch a manner that the capillary is further lowered in a substantiallyvertical direction and toward immediately adjacent to a bonded portionwhere the wire has bonded to the second bonding point, thereby bondingthe wire thereto while causing a face portion located at the firstbonding point side of the capillary to crush at least a portion of thefirst and second folded portions located at the second bonding pointside so as to be overlapped on the wire loop located at the secondbonding point side.

The method of manufacturing a semiconductor device according to thepresent invention can preferably be arranged such that the pressing loadin the first folding step is for bringing the first folded portion intocontact with the upper face on the wire loop.

The present invention is also directed to a wire bonding apparatusincluding a capillary for bonding a first bonding point and a secondbonding point with a wire, the apparatus including: a capillary; a loadsensor for detecting pressing load applied at a tip end of thecapillary; a movement mechanism for moving the capillary in X, Y, and Zdirections; and a control unit for outputting a command signal to themovement mechanism, the control unit including: first bonding means;second bonding means; first folding means; second folding means; thirdbonding means; the first bonding means for bonding a wire fed out of atip end of a capillary to a first bonding point by means of thecapillary; the second bonding means for, after completing the firstbonding, bonding the wire to a second bonding point by means of thecapillary in such a manner that the capillary is raised while feedingthe wire out of the tip end thereof and subsequently looped toward thesecond bonding point along a predetermined trajectory and subsequentlylowered to bond the second bonding point with a face portion located atthe first bonding point side of the capillary, thereby forming a wireloop between the first bonding point and the second bonding point; thefirst folding means for, after completing the second bonding, foldingthe wire to the wire loop by means of the capillary in such a mannerthat the capillary is raised in a substantially vertical direction whilefeeding the wire out of the tip end thereof and subsequently moved in asubstantially horizontal direction and toward the first bonding point bya first predetermined distance, and then the capillary is lowered in asubstantially vertical direction and to the wire loop until the pressingload detected with the load sensor becomes equal to a predeterminedvalue, thereby forming the wire fed out of the tip end of the capillaryinto a first folded portion having a shape that follows the upper faceon the wire loop; the second folding means for, after completing thefirst folding, folding the wire to the first folded portion by means ofthe capillary in such a manner that the capillary is raised in asubstantially vertical direction while further feeding the wire out ofthe tip end thereof and subsequently moved away from the first bondingpoint by a second predetermined distance, and then the capillary issubstantially lowered in a substantially vertical direction, therebyforming the wire further fed out of the tip end of the capillary into asecond folded portion having a shape that follows the upper face on thefirst folded portion; and the third bonding means for, after completingthe second folding, bonding the wire by means of the capillary in such amanner that the capillary is further lowered in a substantially verticaldirection and toward immediately adjacent to a bonded portion where thewire has bonded to the second bonding point, thereby bonding the wirethereto while causing a face portion located at the first bonding pointside of the capillary to crush at least a portion of the first andsecond folded portions located at the second bonding point side so as tobe overlapped on the wire loop located at the second bonding point side.

The wire bonding apparatus according to the present invention canpreferably be arranged such that the pressing load used in the firstfolding means is for bringing the first folded portion into contact withthe upper face of the wire loop.

The present invention is further directed to a method of manufacturing asemiconductor device having a wire loop connecting a first bonding pointand a second bonding point by a wire bonding apparatus having capillary,the method including: a first bonding step; a second bonding step; afirst trampling bonding step; a third folding step; a second tramplingbonding step; the first bonding step of bonding a wire fed out of a tipend of a capillary to a first bonding point by means of the capillary;the second bonding step of, after completing the first bonding step,bonding the wire to a second bonding point by means of the capillary insuch a manner that the capillary is raised while feeding the wire out ofthe tip end thereof and subsequently looped toward the second bondingpoint along a predetermined trajectory and subsequently lowered to bondthe second bonding point with a face portion located at the firstbonding point side of the capillary, thereby forming a wire loop betweenthe first bonding point and the second bonding point; the firsttrampling bonding step of, after completing the second bonding step,trampling the wire to the wire loop by means of the capillary in such amanner that the capillary is raised in a substantially verticaldirection while feeding the wire out of the tip end thereof andsubsequently moved in a substantially horizontal direction and towardthe first bonding point by a first predetermined distance, and then thecapillary is lowered in a substantially vertical direction and onto thewire loop and a bonded portion where the wire has bonded to the secondbonding point to bond the wire fed out of the tip end of the capillary,thereby forming a first trampled portion while folding and tramplingthereon; the third folding step of, after completing the first tramplingbonding step, folding the wire to the first trampled portion by means ofthe capillary in such a manner that the capillary is raised in asubstantially vertical direction while further feeding the wire out ofthe tip end thereof and subsequently moved away from the first bondingpoint by a second predetermined distance, and then the capillary issubstantially lowered in a substantially vertical direction, therebyforming the wire further fed out of the tip end of the capillary into athird folded portion having a shape that follows the upper face on thefirst trampled portion; and the second trampling bonding step of, aftercompleting the third folding step, bonding the wire by means of thecapillary in such a manner that the capillary is further lowered in asubstantially vertical direction and toward immediately adjacent to thebonded portion where the wire has bonded to the second bonding point,thereby bonding the wire thereon while causing a face portion located atthe first bonding side of the capillary to trample at least a portion ofthe third folded portion located at the second bonding point side so asto be overlapped onto the first trampled portion.

In the method of manufacturing a semiconductor device according to thepresent invention, the first trampling bonding step can preferably bearranged such that the wire fed out of the tip end of the capillary isfolded onto the wire loop and the portion where the wire has bonded tothe second bonding point, and trampled until a portion of the surfacethereof is made into a flat.

In the method of manufacturing a semiconductor device according to thepresent invention, the second trampling bonding step can preferably bearranged such that at least a portion of the third folded portionlocated at the second bonding point side is trampled onto the firsttrampled portion with the face portion located at the first bondingpoint side of the capillary until a portion of the surface thereof ismade into a flat.

The method of manufacturing a semiconductor device according to thepresent invention can preferably be arranged such that the capillary isconfigured to be vibrated ultrasonically, and that in the first bondingstep, second bonding step, first trampling bonding step, and secondtrampling bonding step, the capillary is vibrated ultrasonically duringbonding operation.

The method of manufacturing a semiconductor device according to thepresent invention can preferably further include a wire cutoff step of,after the second trampling bonding step, raising the capillary with thewire in a substantially vertical direction while clamping the wire witha clamper, thereby cutting off the wire.

The present invention is also directed to a wire bonding apparatusincluding a capillary for bonding a first bonding point and a secondbonding point with a wire, the apparatus including: a capillary; amovement mechanism for moving the capillary in X, Y, and Z directions;and a control unit for outputting a command signal to the movementmechanism, the control unit including: first bonding means; secondbonding means; first trampling bonding means; third folding means;second trampling bonding means; the first bonding means for bonding awire fed out of a tip end of a capillary to a first bonding point bymeans of the capillary; the second bonding means for, after completingthe first bonding, bonding the wire to a second bonding point by meansof the capillary in such a manner that the capillary is raised whilefeeding the wire out of the tip end thereof and subsequently loopedtoward the second bonding point along a predetermined trajectory andsubsequently lowered to bond the second bonding point with a faceportion located at the first bonding point side of the capillary,thereby forming a wire loop between the first bonding point and thesecond bonding point; the first trampling bonding means for, aftercompleting the second bonding, trampling the wire loop to the wire loopby means of the capillary in such a manner that the capillary is raisedin a substantially vertical direction while feeding the wire out of thetip end thereof and subsequently moved in a substantially horizontaldirection and toward the first bonding point by a first predetermineddistance, and then the capillary is lowered in a substantially verticaldirection and onto the wire loop and a bonded portion where the wire hasbonded to the second bonding point to bond the wire fed out of the tipend of the capillary, thereby forming a first trampled portion whilefolding and trampling thereon; the third folding means for, aftercompleting the first trampling bonding, folding the wire to the firsttrampled portion by means of the capillary in such a manner that thecapillary is raised in a substantially vertical direction while furtherfeeding the wire out of the tip end thereof and subsequently moved awayfrom the first bonding point by a second predetermined distance, andthen the capillary is substantially lowered in a substantially verticaldirection, thereby forming the wire further fed out of the tip end ofthe capillary into a third folded portion having a shape that followsthe upper face on the first trampled portion; and the second tramplingbonding means for, after completing the third folding, bonding the wireby means of the capillary in such a manner that the capillary is furtherlowered in a substantially vertical direction and toward immediatelyadjacent to the bonded portion where the wire has bonded to the secondbonding point, thereby bonding the wire thereto while causing a faceportion located at the first bonding side of the capillary to trample atleast a portion of the third folded portion located at the secondbonding point side so as to be overlapped onto the first trampledportion.

The present invention offers the advantage of providing a compact wireloop with a great strength of bonding.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Exemplary embodiments of the present invention will be described indetail based on the following figures, wherein:

FIG. 1 is a systematic diagram illustrating the configuration of a wirebonding apparatus according to an exemplary embodiment of the presentinvention;

FIG. 2 illustrates a state of a load sensor installed in the wirebonding apparatus according to an exemplary embodiment of the presentinvention;

FIG. 3 is a flow chart illustrating an operation of the wire bondingapparatus according to an exemplary embodiment of the present invention;

FIG. 4A illustrates an operation of a first bonding step in a method ofmanufacturing a semiconductor device according to an exemplaryembodiment of the present invention;

FIG. 4B illustrates another operation of the first bonding step in themethod of manufacturing a semiconductor device according to an exemplaryembodiment of the present invention;

FIG. 4C illustrates still another operation of the first bonding step inthe method of manufacturing a semiconductor device according to anexemplary embodiment of the present invention;

FIG. 4D illustrates a further operation of the first bonding step in themethod of manufacturing a semiconductor device according to an exemplaryembodiment of the present invention;

FIG. 4E illustrates an operation of a second bonding step in the methodof manufacturing a semiconductor device according to an exemplaryembodiment of the present invention;

FIG. 4F illustrates another operation of the second bonding step in themethod of manufacturing a semiconductor device according to an exemplaryembodiment of the present invention;

FIG. 4G illustrates still another operation of the second bonding stepin the method of manufacturing a semiconductor device according to anexemplary embodiment of the present invention;

FIG. 4H illustrates an operation of a first folding step in the methodof manufacturing a semiconductor device according to an exemplaryembodiment of the present invention;

FIG. 4J illustrates another operation of the first folding step in themethod of manufacturing a semiconductor device according to an exemplaryembodiment of the present invention;

FIG. 4K illustrates an operation of a second folding step in the methodof manufacturing a semiconductor device according to an exemplaryembodiment of the present invention;

FIG. 4L illustrates an operation of a third bonding step in the methodof manufacturing a semiconductor device according to an exemplaryembodiment of the present invention;

FIG. 4M illustrates a wire cutoff operation in the method ofmanufacturing a semiconductor device according to an exemplaryembodiment of the present invention;

FIG. 5 illustrates the vicinity of a lead during an operation of thefirst folding step in the method of manufacturing a semiconductor deviceaccording to an exemplary embodiment of the present invention;

FIG. 6 illustrates the vicinity of the lead during an operation of thesecond folding step in the method of manufacturing a semiconductordevice according to an exemplary embodiment of the present invention;

FIG. 7 illustrates the vicinity of the lead during another operation ofthe second folding step in the method of manufacturing a semiconductordevice according to an exemplary embodiment of the present invention;

FIG. 8 illustrates the vicinity of the lead during an operation of thethird bonding step in the method of manufacturing a semiconductor deviceaccording to an exemplary embodiment of the present invention;

FIG. 9 illustrates the vicinity of the lead during a wire cutoffoperation in the method of manufacturing a semiconductor deviceaccording to an exemplary embodiment of the present invention;

FIG. 10 illustrates a movement locus of a capillary in the method ofmanufacturing a semiconductor device according to an exemplaryembodiment of the present invention;

FIG. 11 is a perspective view illustrating a terminal of a wire loopcloser to the lead according to an exemplary embodiment of the presentinvention;

FIG. 12 is a systematic diagram illustrating the configuration of a wirebonding apparatus according to an exemplary embodiment of the presentinvention;

FIG. 13 is a flow chart illustrating an operation of the wire bondingapparatus according to an exemplary embodiment of the present invention;

FIG. 14 illustrates the vicinity of a lead during an operation of afirst trampling bonding step in a method of manufacturing asemiconductor device according to an exemplary embodiment of the presentinvention;

FIG. 15 illustrates the vicinity of the lead during another operation ofthe first trampling bonding step in the method of manufacturing asemiconductor device according to an exemplary embodiment of the presentinvention;

FIG. 16 illustrates the vicinity of the lead during an operation of athird folding step in the method of manufacturing a semiconductor deviceaccording to an exemplary embodiment of the present invention;

FIG. 17 illustrates the vicinity of the lead during another operation ofthe third folding step in the method of manufacturing a semiconductordevice according to an exemplary embodiment of the present invention;

FIG. 18 illustrates the vicinity of the lead during an operation of asecond trampling bonding step in the method of manufacturing asemiconductor device according to an exemplary embodiment of the presentinvention;

FIG. 19 illustrates the vicinity of the lead during a wire cutoffoperation in the method of manufacturing a semiconductor deviceaccording to an exemplary embodiment of the present invention;

FIG. 20 illustrates a movement locus of a capillary in the method ofmanufacturing a semiconductor device according to an exemplaryembodiment of the present invention; and

FIG. 21 is a perspective view illustrating a terminal of a wire loopcloser to the lead according to an exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

A wire bonding apparatus 10 according to an exemplary embodiment of thepresent invention will hereinafter be described in detail with referenceto the accompanying drawings. In FIG. 1, each alternate long and shortdash line represents a signal line. As shown in FIG. 1, the wire bondingapparatus 10 includes a bonding head 19 placed on an XY table 20 and abonding arm 13 attached to the bonding head 19. The bonding arm 13 isconfigured to be driven and rotated about a center of rotation with aZ-directional motor and has an ultrasonic horn 13 b attached at aleading end thereof, and a front end of the ultrasonic horn 13 b isconfigured to move arcuately toward and away from a pad surface of asemiconductor chip 72 serving as a bonding surface. Also the front endof the ultrasonic horn 13 b is configured to move vertically in the Zdirection in the vicinity of (immediately adjacent to) the pad surfaceof the semiconductor chip 72 or the surface of a lead frame 71. At thefront end of the ultrasonic horn 13 b, there is attached a capillary 16serving as a bonding tool. The XY table 20 and the bonding head 19configure a movement mechanism 18 in which the bonding head 19 can bemoved freely with the XY table 20 within a plane (XY plane) lying alongthe bonding surface, whereby driving the bonding arm 13 attached to themovement mechanism 18 using the Z-directional motor allows the front endof the ultrasonic horn 13 b that is attached at the leading end of thebonding arm 13 and the capillary 16 attached at the front end of theultrasonic horn 13 b to be moved freely in the X, Y, and Z directions.On the leading end side of the bonding arm 13 with respect to the XYtable 20, there is provided a bonding stage 14 for sucking and fixingthe lead frame 71 thereto.

As shown in FIG. 2, the bonding arm 13 has an approximately rectangularparallelepiped shape extending in a direction along the central axis 13d of the ultrasonic horn 13, and has a front end portion 13 a includinga flange mounting surface 13 m and a rear end portion 13 r including acenter of rotation (not shown). In a portion of the bonding arm 13closer to (located at the side of) the bonding stage 14, there isprovided a recess 13 g for housing therein an ultrasonic vibrator 15 tobe connected to the ultrasonic horn 13 b. A flange 13 n is provided at anode of the vibration of the ultrasonic horn 13 b and fixed using a bolt13 q to the flange mounting surface 13 m in the front end portion 13 a.The front and rear end portions 13 a and 13 r are connected via a thinplate-like connection 13 h provided at a height position (in the Zdirection) including the central axis 13 d of the ultrasonic horn 13 b.Between the front and rear end portions 13 a and 13 r of the bonding arm13, narrow slits 13 f and 13 k are formed, respectively, on the side ofthe bonding stage 14 and its opposite side with respect to theconnection 13 h. In a Z-directional upper portion of the bonding arm 13farther from the bonding stage 14, there is provided a groove 13 e forfitting a load sensor 25 therein. The groove 13 e is provided in anopposed manner between the front and rear end portions 13 a and 13 r ofthe bonding arm 13. The load sensor 25 fitted in the groove 13 e issandwiched in between the front and rear end portions 13 a and 13 r ofthe bonding arm 13 and pressurized using screws 13 p inserted throughthe front end portion 13 a into the rear end portion 13 r. The centralaxis 13 c of the load sensor 25 is offset from the central axis 13 d ofthe ultrasonic horn 13 b by a distance of L in the Z direction.

As shown in FIG. 1, the capillary 16 has an opened cylindrical structurewith a conical tip end and has a central wire hole through which a wire81 made of gold or the like can be inserted. The wire 81 is suppliedfrom a spool 11 mounted on the bonding head 19. The ultrasonic horn 13 bhas a feature of providing ultrasonic energy generated at the ultrasonicvibrator 15 to the capillary 16 to press and bond the wire 81 insertedthrough the capillary 16 to the pad surface of the semiconductor chip 72serving as a bonding surface and a lead on the lead frame 71. In thevicinity of (immediately adjacent to) the bonding stage 14, there isprovided a discharge torch 26 for heating and forming a wire extendingout of the tip end of the capillary 16 into an initial ball.

The bonding head 19 is provided with a clamper 17 for clamping andreleasing the wire 81 inserted through the capillary 16. The clamper 17is configured to move in the X, Y, and Z directions in conjunction withthe bonding arm 13. The wire bonding apparatus 10 includes a clamperopening and closing mechanism 27, and the clamper 17 is configured to beopened and closed by the operation of the clamper opening and closingmechanism 27.

As shown in FIG. 1, the wire bonding apparatus 10 includes a controlunit 30 having a CPU built-in to detect the position and control theoperation of each component for connection between the semiconductorchip 72 and the lead frame 71 with the wire 81. The XY table 20 isprovided with XY position detecting means for detecting the XY positionof the bonding head 19. Also, the bonding head 19 is provided withcapillary height detecting means 29 for detecting the angle of rotationof the bonding arm 13 about the center of rotation to detect theZ-directional height of the tip end of the capillary 16. The capillaryheight detecting means 29 can not detect the angle of rotation, but candirectly detect the position of the leading end of the bonding arm 13 orthe tip end of the capillary 16. The capillary height detecting means 29can also be either contactless or contact type.

A camera 28 is attached to the bonding head 19 as imaging means foracquiring images of the semiconductor chip 72, lead frame 71, etc. Thebonding head 19 is configured to position the capillary 16 in the X andY directions based on images acquired using the camera 28. The camera 28can include only an imaging element and a lens with no aperture orshutter mechanism as long as capable of acquiring image signals.

Detection signals from the capillary height detecting means 29 and theload sensor 25 are configured to be fed to the control unit 30,respectively, via a capillary height detection interface 42 and a loadsensor interface 46 through a data bus 32 connected to the control unit30. Also, the movement mechanism 18, which is configured with the XYtable 20 and the bonding head 19, clamper opening and closing mechanism27, ultrasonic vibrator 15, and discharge torch 26 are connected throughthe data bus 32 to the control unit 30, respectively, via a movementmechanism interface 44, a clamper opening and closing mechanisminterface 41, an ultrasonic vibrator interface 43, and a ball formingmeans interface 45. These components are each configured to operatebased on a command from the CPU-built-in control unit 30.

A storage unit 34 is connected to the data bus 32. The storage unit 34,which holds control data required for position detecting processing andcontrol command output operations performed by the control unit 30, isconfigured to output control data to the control unit 30 based on acommand from the control unit 30 and to store and hold signal data fedtherein. The control unit 30, data bus 32, storage unit 34, andinterfaces 41 to 46 integrally configure a computer 60. The storage unit34 stores therein not only control data but also control programs foroverall bonding control, a first bonding program serving as firstbonding means, a second bonding program serving as second bonding means,a first folding program serving as first folding means, a second foldingprogram serving as second folding means, and a third bonding programserving as third bonding means.

Next will be described a process for manufacturing a semiconductordevice through a wire bonding operation by the thus arranged wirebonding apparatus 10. The control unit 30 first retrieves the overallcontrol programs, first bonding program, second bonding program, firstfolding program, second folding program, third bonding program, andcontrol data, which are stored in the storage unit 34, to store in itsbuilt-in memory. As shown in FIG. 4A, in an initial state, a tail wire82 extends out of the tip end of the capillary 16 and the clamper 17 isclosed.

As indicated by Step S101 in FIG. 3, the control unit 30 issues acommand to form an initial ball. Based on this command, a signal fromthe movement mechanism interface 44 is output to the XY table 20. The XYtable 20 then moves the bonding head 19 to cause the tip end of thecapillary 16 to come in the vicinity of (immediately adjacent to) thedischarge torch 26. When the capillary 16 comes in the vicinity of(immediately adjacent to) the discharge torch 26, a discharge is formedbetween the discharge torch 26 and the tail wire 82 extending out of thetip end of the capillary 16 based on a signal from the ball formingmeans interface 45, so that the tail wire 82 is formed into a sphericalinitial ball 83, as shown in FIG. 4B.

As indicated by Step S102 in FIG. 3 and shown in FIG. 4C, the controlunit 30 issues a command to move the capillary 16 over a pad 73 on thesemiconductor chip 72 serving as a first bonding point. Based on thiscommand, a signal from the movement mechanism interface 44 is output tothe XY table 20. The XY table 20 then moves the bonding head 19 to causethe center of the capillary 16 to come just above the pad 73.

The control unit 30 then performs a first bonding step. As indicated byStep S103 in FIG. 3, the control unit 30 issues a command to lower thecapillary 16. Based on this command, a signal from the movementmechanism interface 44 is output to the bonding head 19. TheZ-directional motor installed in the bonding head 19 is then driven torotate the bonding arm 13 and thereby lower the tip end of the capillary16 on the pad 73. Also based on this command, a signal from the clamperopening and closing mechanism interface 41 is output to the clamperopening and closing mechanism 27. The clamper opening and closingmechanism 27 then opens the clamper 17. As indicated by Step S104 inFIG. 3 and shown in FIG. 4D, the initial ball 83 formed at the tip endof the capillary 16 is pressed onto the pad 73 and, based on a signalfrom the ultrasonic vibrator interface 43, the ultrasonic vibrator 15 isdriven to vibrate the capillary 16 and to bond the initial ball 83 ontothe pad 73 as a bonded ball 84 (first bonding).

Following the first bonding step, the control unit 30 performs a secondbonding step. As indicated by Step S105 in FIG. 3, the control unit 30issues a command to raise the capillary 16 with the clamper 17 beingopened. Based on this command, a signal from the movement mechanisminterface 44 is output to the bonding head 19. The Z-directional motorinstalled in the bonding head 19 is then driven to rotate the bondingarm 13 and thereby raise the tip end of the capillary 16 from the pad73, as shown in FIG. 4E. At the same time, the signal from the movementmechanism interface 44 is output to the XY table 20. The capillary 16then moves horizontally away from a lead 74 on the lead frame 71 by apredetermined distance. Thereafter, the capillary 16 is further raisedto a predetermined height. In this case, since the clamper 17 is opened,the wire 81 is fed out of the tip end of the capillary 16.

When the capillary 16 is raised to the predetermined height, the controlunit 30 issues a command to loop the capillary 16 to a point over thelead 74 serving as a second bonding point with the clamper 17 beingopened, as indicated by Step S106 in FIG. 3. Based on this command, asignal from the movement mechanism interface 44 is output to the bondinghead 19 and the XY table 20. As shown in FIG. 4F, the capillary 16 thenmoves toward the lead 74 in a looped manner along a predetermined locus(trajectory). Also during this looping, since the clamper 17 is opened,the wire 81 is fed out of the tip end of the capillary 16. Thepredetermined locus (trajectory) here means a triangular loop,trapezoidal loop, M-shaped loop locus (trajectory), or the like.

When the capillary 16 comes over the lead 74, the control unit 30 issuesa command to lower the capillary 16, as indicated by Step S107 in FIG.3. Based on this command, a signal from the movement mechanism interface44 is output to the bonding head 19. The Z-directional motor installedin the bonding head 19 is then driven to rotate the bonding arm 13 andthereby lower the tip end of the capillary 16 on the lead 74. Asindicated by Step S108 in FIG. 3 and shown in FIG. 4G, the wire 81 ispressed against the lead 74 with the tip end of the capillary 16 and,based on a signal from the ultrasonic vibrator interface 43, theultrasonic vibrator 15 is driven to vibrate the capillary 16 and to bondthe wire 81 onto the lead 74 (second bonding). The second bonding formsa wire loop 85 for connection between the pad 73 serving as the firstbonding point and the lead 74 serving as the second bonding point, asshown in FIG. 4G.

Following the formation of the wire loop 85, the control unit 30performs a first folding step. As indicated by Step S109 in FIG. 3 andshown in FIG. 4H, the control unit 30 issues a command to raise thecapillary 16 by a height of H₁ with the clamper 17 being opened. Basedon this command, a signal from the movement mechanism interface 44 isoutput to the bonding head 19. The Z-directional motor installed in thebonding head 19 is then driven to rotate the bonding arm 13 and therebyraise the capillary 16. The control unit 30 acquires a signal from thecapillary height detecting means 29 via the capillary height detectioninterface 42 to monitor if the tip end of the capillary 16 is raised tothe height H₁. If it is determined based on the signal from thecapillary height detecting means 29 that the tip end of the capillary 16is raised to the height H₁, the control unit 30 then stops raising thecapillary 16. In this case, since the clamper 17 is opened, the wire 81is fed out of the tip end of the capillary 16.

As indicated by Step S110 in FIG. 3 and shown in FIG. 4H, the controlunit 30 then issues a command to move the capillary 16 horizontallytoward the pad 73 by a first distance of L₁. Based on this command, asignal from the movement mechanism interface 44 is output to the XYtable 20. The XY table 20 then moves the capillary 16 toward the pad 73.The control unit 30 localizes the capillary 16 based on a signal fromthe XY position detecting means provided in the XY table 20 fordetection of the XY position of the bonding head 19 to monitor if thecapillary 16 is moved by the first distance L₁. If it is determined thatthe capillary 16 is moved by the first distance L₁, the control unit 30then stops moving the capillary 16 horizontally. When the horizontalmovement of the capillary 16 is stopped, the wire fed out of the tip endof the capillary 16 is formed in a first folded portion 86 folded fromthe lead 74 toward the pad 73.

As indicated by Step S111 in FIG. 3 and shown in FIG. 4J, the controlunit 30 issues a command to lower the capillary 16. Based on thiscommand, a signal from the movement mechanism interface 44 is output tothe bonding head 19. The Z-directional motor installed in the bondinghead 19 is then driven to rotate the bonding arm 13 and thereby start tolower the capillary 16. When the capillary 16 is lowered, the pressingload on the capillary 16 increases gradually due to the force ofrepulsion by the first folded portion 86. The control unit 30 acquiresthe pressing load on the capillary 16 based on a signal from the loadsensor 25. When the capillary 16 is further lowered, the lower face ofthe first folded portion 86 is brought into contact with the upper faceof the wire loop 85, as shown in FIG. 5. This causes the pressing loadon the capillary 16 to further increase. Then, as indicated by Step S112in FIG. 3, when the pressing load detected with the load sensor 25becomes equal to a predetermined value, the control unit 30 issues acommand to stop lowering the capillary, as indicated by Step S113 inFIG. 3. Based on this command, the lowering of the capillary 16 isstopped and the first folding step is completed.

As shown in FIG. 5, in the state where the lowering of the capillary 16is stopped, the first folded portion 86 is in contact with the upperface of the wire loop 85, which extends obliquely downward to the bondedportion 85 a where bonded to the lead 74, and presses the wire loop 85downward, so that the pressing load detected with the load sensor 25becomes equal to the predetermined value. The wire loop 85 is slightlypressed downward, but approximately maintains its original shape. Thefirst folded portion 86 extends in an S-shaped arc along the upper faceof the wire loop 85 from the point 86 a where the center of thecapillary 16 is positioned during the second bonding of the wire 81 tothe lead 74 toward the pad 73, and further extends in a bent manner fromthe contact point 86 b with the wire loop 85 toward the capillary 16above. Also, in this exemplary embodiment, neither the face portion 16 anor the outer radius portion 16 b at the tip end of the capillary 16 isin contact with the wire loop 85.

Following the first folding step, the control unit 30 performs a secondfolding step. As indicated by Step S114 in FIG. 3 and shown in FIG. 4K,the control unit 30 issues a command to raise the tip end of thecapillary 16 to a height of H₂ with the clamper 17 being opened. Basedon this command, a signal from the movement mechanism interface 44 isoutput to the bonding head 19. The Z-directional motor installed in thebonding head 19 is then driven to rotate the bonding arm 13 and therebyraise the capillary 16. The control unit 30 acquires a signal from thecapillary height detecting means 29 via the capillary height detectioninterface 42 to monitor if the tip end of the capillary 16 is raised tothe height H₂. If it is determined based on the signal from thecapillary height detecting means 29 that the tip end of the capillary 16is raised to the height H₂, the control unit 30 then stops raising thecapillary 16. In this case, since the clamper 17 is opened, the wire 81is fed out of the tip end of the capillary 16.

As indicated by Step S115 in FIG. 3 and shown in FIG. 4K, the controlunit 30 issues a command to move the capillary 16 horizontally away fromthe pad 73 by a second distance of L₂ that is greater than the firstdistance L₁ of the horizontal movement in the first folding step. Basedon this command, a signal from the movement mechanism interface 44 isoutput to the XY table 20. The XY table 20 then moves the capillary 16away from the pad 73, that is, toward the lead 74. The control unit 30localizes the capillary 16 based on a signal from the XY positiondetecting means provided in the XY table 20 for detection of the XYposition of the bonding head 19 to monitor if the capillary 16 is movedby the second distance L₂. If it is determined that the capillary 16 ismoved by the second distance L₂, the control unit 30 then stops movingthe capillary 16 horizontally. When the horizontal movement of thecapillary 16 is stopped, the wire fed out of the tip end of thecapillary 16 is formed in a second folded portion 87 folded from thefirst folded portion 86 toward the lead 74, as shown in FIG. 6. Sincethe second distance L₂ of the horizontal movement of the capillary 16 isgreater than the first distance L₁ in the first folding step, in thestate where the horizontal movement of the capillary 16 is stopped, thecenter of the capillary 16 is on the opposite side of the pad 73 withrespect to the contact point 86 a of the first folded portion 86 withthe lead 74 where the center of the capillary 16 is positioned duringthe second bonding, as shown in FIG. 6. That is, the center of thecapillary 16 is positioned beyond the bonded portion 85 a at the secondbonding point.

As indicated by Step S116 in FIG. 3, the control unit 30 issues acommand to perform a third bonding step. Based on this command, a signalfrom the movement mechanism interface 44 is output to the bonding head19. The Z-directional motor installed in the bonding head 19 is thendriven to rotate the bonding arm 13 and thereby start to lower thecapillary 16. When the capillary 16 is lowered, the second foldedportion 87 is bent to be overlaid on the first folded portion 86, asshown in FIG. 7. Then the face portion 16 a or the outer radius portion16 b of the capillary 16 closer to (located at the side of) the pad 73comes into contact with a lateral face of the second folded portion 87,as shown in FIG. 7. Thus, the second folded portion 87 is further foldedwith the face portion 16 a or the outer radius portion 16 b.

As shown in FIGS. 4L and 8, when the capillary 16 is further lowered,the face portion 16 a and the outer radius portion 16 b of the capillary16 closer to (located at the side of) the pad 73 press and deform thefirst and second folded portions 86 and 87, so that the upper faces ofthe portions are shaped according to the face portion 16 a and the outerradius portion 16 b of the capillary 16. At the same time, the endportions of the first and second folded portions 86 and 87 farther fromthe pad 73 are bonded to a point 87 a on the lead 74 adjacent to thepoint 86 a in such a manner that a portion of the first and secondfolded portions 86 and 87 is overlaid on the bonded portion 85 a of thewire loop 85 where bonded to the lead 74. After the first and secondfolded portions 86 and 87 are bonded to the lead 74, the third bondingstep is completed.

After the third bonding step, the control unit 30 issues a command toraise the capillary 16 with the clamper 17 being opened, as indicated byStep S117 in FIG. 3. Based on this command, a signal from the movementmechanism interface 44 is output to the bonding head 19. TheZ-directional motor installed in the bonding head 19 is then driven torotate the bonding arm 13 and thereby raise the capillary 16. In thiscase, since the clamper 17 is opened, the wire 81 is fed out of the tipend of the capillary 16.

After the capillary 16 is raised by a predetermined distance, thecontrol unit 30 issues a wire cutoff command, as indicated by Step S118in FIG. 3. Based on this command, a signal from the clamper opening andclosing mechanism interface 41 is output to the clamper opening andclosing mechanism 27. The clamper opening and closing mechanism 27 thencloses the clamper 17. When the capillary 16 is further raised with theclamper 17 being closed, the wire 81 is cut off, as shown in FIGS. 4Mand 9, to be a state where a tail wire 82 extends out of the tip end ofthe capillary 16. Also, at the point 87 a on the lead 74 where thecenter of the capillary 16 is positioned during the third bonding, thereis formed a roundly raised wire cutoff residual 87 d.

FIG. 10 schematically illustrates the locus (trajectory) of the tip endof the capillary 16 through the first and second folding steps and thethird bonding step described above. As shown in FIG. 10, in the firstfolding step, the tip end of the capillary 16 is raised by the height H₁from the point 86 a where the center of the capillary 16 is positionedduring the second bonding on the lead 74 to the point “p”, and thenmoved horizontally by the first distance L₁ toward the pad 73, andlowered to the point “r” where the load detected with the load sensor 25becomes equal to the predetermined value. In the second folding step,the tip end of the capillary 16 is raised from the point “r” to theheight H₂, and then moved horizontally away from the pad 73, that is,toward the lead 74 by the second distance L₂, which is slightly greaterthan the first distance L₁. In the third bonding step, the center of thecapillary 16 is aligned with the point 87 a adjacent to the point 86 aon the opposite side of the pad 73 with respect to the point 86 a, andthen lowered to the point 87 a on the lead 74.

FIG. 11 illustrates the shape of the terminal of the wire loop 85 closerto (located at the side of) the lead 74 formed through theabove-described bonding operation. As shown in FIG. 11, the terminalcloser to (located at the side of) the lead 74 is formed by the endportions of the first and second folded portions 86 and 87 farther fromthe pad 73 being pressed and deformed in an overlaid manner on thebonded portion 85 a of the wire loop 85 where bonded to the lead 74. Thesurface of the end portions of the first and second folded portions 86and 87 farther from the pad 73 is formed in a cylindrical recess 87 efollowing the shape of the tip end of the capillary 16. The end portionof the recess 87 e farther from the pad 73 is the roundly raised wirecutoff residual 87 d. The first and second folded portions 86 and 87extend in a roll-up manner from the wire cutoff residual 87 d toward thepad 73, and the end portions 86 c and 87 c thereof closer to (located atthe side of) the pad 73 are folded to be a round end.

As described heretofore, in this exemplary embodiment, the first andsecond folded portions 86 and 87 are bonded to the terminal of the wireloop 85 closer to (located at the side of) the lead 74 in an overlaidmanner, whereby the strength of bonding between the wire loop 85 and thelead 74 is increased. Also, a portion of the first and second foldedportions 86 and 87 is pressed and deformed with the tip end of thecapillary on the bonded portion 85 a of the wire loop 85 where bonded tothe lead 74, resulting in a compact shape. At the same time, the firstfolded portion 86 can be folded to follow the shape of the wire loop 85,while maintaining the shape of the wire loop 85, by pressing thecapillary 16 downward until the pressing load on the capillary 16becomes equal to the predetermined value in the first folding step,whereby even a short wire can be formed reliably into a folded shape,the shape of the terminal of the compact wire loop 85 can be formedstably, and the thickness of the bonded portion where bonded to the lead74 can be increased, which allows for preventing heel crack effectively.

Although the second distance L₂ of the horizontal movement is greaterthan the first distance L₁ of the horizontal movement in the firstfolding step in the above description of this exemplary embodiment, thesecond distance L₂ of the horizontal movement can be equal to or smallerthan the first distance L₁ of the horizontal movement in the firstfolding step.

Next will be described another exemplary embodiment of the presentinvention with reference to FIGS. 12 to 21. Components identical tothose in the exemplary embodiment described with reference to FIGS. 1 to11 are designated by the same reference numerals to omit the descriptionthereof.

As shown in FIG. 12, unlike the wire bonding apparatus 10 describedabove with reference to FIG. 1, the storage unit 34 in the wire bondingapparatus 100 according to this exemplary embodiment stores therein notonly control data but also control programs for overall bonding control,a first bonding program serving as first bonding means, a second bondingprogram serving as second bonding means, a first trampling bondingprogram serving as first trampling bonding means, a third foldingprogram serving as third folding means, and a second trampling bondingprogram serving as second trampling bonding means. The other componentsare configured in the same manner as in the wire bonding apparatus 10described with reference to FIG. 1.

Next will be described a process for manufacturing a semiconductordevice through a wire bonding operation by the thus arranged wirebonding apparatus 100 according to this exemplary embodiment. Thecontrol unit 30 first retrieves the overall control programs, firstbonding program, second bonding program, first trampling bondingprogram, third folding program, second trampling bonding program, andcontrol data, which are stored in the storage unit 34, to store in itsbuilt-in memory. As shown in FIG. 4A, in an initial state, a tail wire82 extends out of the tip end of the capillary 16 and the clamper 17 isclosed. The first and second bonding steps shown in FIGS. 4A to 4G arethe same as in the above-described exemplary embodiment, so thedescription thereof will be omitted to begin from the first tramplingbonding step.

As indicated by Step S209 in FIG. 13 and shown in FIG. 4H, the controlunit 30 issues a command to raise the capillary 16 by a height of H₁with the clamper 17 being opened in the first trampling bonding step.Based on this command, a signal from the movement mechanism interface 44is output to the bonding head 19. The Z-directional motor installed inthe bonding head 19 is then driven to rotate the bonding arm 13 andthereby raise the capillary 16. The control unit 30 acquires a signalfrom the capillary height detecting means 29 via the capillary heightdetection interface 42 to monitor if the tip end of the capillary 16 israised to the height H₁. If it is determined based on the signal fromthe capillary height detecting means 29 that the tip end of thecapillary 16 is raised to the height H₁, the control unit 30 then stopsraising the capillary 16. In this case, since the clamper 17 is opened,the wire 81 is fed out of the tip end of the capillary 16.

As indicated by Step S210 in FIG. 13 and shown in FIG. 4H, the controlunit 30 then issues a command to move the capillary 16 horizontallytoward the pad 73 by a first distance of L₁. Based on this command, asignal from the movement mechanism interface 44 is output to the XYtable 20. The XY table 20 then moves the capillary 16 toward the pad 73.The control unit 30 localizes the capillary 16 based on a signal fromthe XY position detecting means provided in the XY table 20 fordetection of the XY position of the bonding head 19 to monitor if thecapillary 16 is moved by the first distance L₁. If it is determined thatthe capillary 16 is moved by the first distance L₁, the control unit 30then stops moving the capillary 16 horizontally. When the horizontalmovement of the capillary 16 is stopped, the wire fed out of the tip endof the capillary 16 is formed in a first folded portion 86 folded fromthe lead 74 toward the pad 73.

As indicated by Step S211 in FIG. 13 and shown in FIG. 4J, the controlunit 30 issues a command to lower the capillary 16. Based on thiscommand, a signal from the movement mechanism interface 44 is output tothe bonding head 19. The Z-directional motor installed in the bondinghead 19 is then driven to rotate the bonding arm 13 and thereby start tolower the capillary 16. When the capillary 16 is lowered, the lower faceof the first folded portion 86 is brought into contact with the upperface of the wire loop 85, as shown in FIG. 14. At this point of time,the wire loop 85 extends obliquely downward to the bonded portion 85 awhere bonded to the lead 74. The first folded portion 86 extends in aslightly S-shaped arc along the upper face of the wire loop 85 from thepoint 86 a where the center of the capillary 16 is positioned during thesecond bonding of the wire 81 to the lead 74 toward the pad 73, andfurther extends in a bent manner from the contact point 86 b with thewire loop 85 toward the capillary 16 above. In the state shown in FIG.14, neither the face portion 16 a nor the outer radius portion 16 b atthe tip end of the capillary 16 is in contact with the wire loop 85.

As indicated by Step S212 in FIG. 13 and shown in FIG. 15, when thecapillary 16 is then further lowered, the face portion 16 a of thecapillary 16 presses the first folded portion 86 onto the wire loop 85and the bonded portion 85 a at the second bonding point. The firstfolded portion 86 and the wire loop 85 are trampled in an overlaidmanner until the surface of the first folded portion 86 becomes flat(first trampling bonding) to form a first trampled portion 86 d shown inFIG. 15. In this case, the first folded portion 86 can be pressed withthe tip end of the capillary 16, and the ultrasonic vibrator 15 can bedriven based on a signal from the ultrasonic vibrator interface 43 tovibrate the capillary 16. After forming the first trampled portion 86 d,the control unit 30 completes the first trampling bonding step. It isnoted that in the first trampling bonding step, the tip end of thecapillary 16 can be lowered to a height from the surface of the lead 74about half the diameter of the wire 81 to be bonded.

Following the first trampling bonding step, the control unit 30 performsa third folding step. As indicated by Step S213 in FIG. 13 and shown inFIG. 4K, the control unit 30 issues a command to raise the tip end ofthe capillary 16 to a height of H₂ with the clamper 17 being opened.Based on this command, a signal from the movement mechanism interface 44is output to the bonding head 19. The Z-directional motor installed inthe bonding head 19 is then driven to rotate the bonding arm 13 andthereby raise the capillary 16. The control unit 30 acquires a signalfrom the capillary height detecting means 29 via the capillary heightdetection interface 42 to monitor if the tip end of the capillary 16 israised to the height H₂. If it is determined based on the signal fromthe capillary height detecting means 29 that the tip end of thecapillary 16 is raised to the height H₂, the control unit 30 then stopsraising the capillary 16. In this case, since the clamper 17 is opened,the wire 81 is fed out of the tip end of the capillary 16.

As indicated by Step S214 in FIG. 13 and shown in FIG. 4K, the controlunit 30 issues a command to move the capillary 16 horizontally away fromthe pad 73 by a second distance of L₂ that is greater than the firstdistance L₁ of the horizontal movement in the first trampling bondingstep. Based on this command, a signal from the movement mechanisminterface 44 is output to the XY table 20. The XY table 20 then movesthe capillary 16 away from the pad 73, that is, toward the lead 74. Thecontrol unit 30 localizes the capillary 16 based on a signal from the XYposition detecting means provided in the XY table 20 for detection ofthe XY position of the bonding head 19 to monitor if the capillary 16 ismoved by the second distance L₂. If it is determined that the capillary16 is moved by the second distance L₂, the control unit 30 then stopsmoving the capillary 16 horizontally. When the horizontal movement ofthe capillary 16 is stopped, the wire fed out of the tip end of thecapillary 16 is formed in a third folded portion 88 folded from thefirst trampled portion 86 d toward the lead 74, as shown in FIG. 16.Since the second distance L₂ of the horizontal movement of the capillary16 is greater than the first distance L₁ in the first trampling bondingstep, in the state where the horizontal movement of the capillary 16 isstopped, the center of the capillary 16 is on the opposite side of thepad 73 with respect to the point 86 a where the center of the capillary16 is positioned during the second bonding, as shown in FIG. 16. Thatis, the center of the capillary 16 is positioned beyond the bondedportion 85 a at the second bonding point. After moving the capillary 16to the position, the control unit 30 completes the third folding step.

As indicated by Step S215 in FIG. 13, after the third folding step, thecontrol unit 30 issues a command to perform a second trampling bondingstep. Based on this command, a signal from the movement mechanisminterface 44 is output to the bonding head 19. The Z-directional motorinstalled in the bonding head 19 is then driven to rotate the bondingarm 13 and thereby start to lower the capillary 16. When the capillary16 is lowered, the third folded portion 88 is bent over the firsttrampled portion 86 d, as shown in FIG. 17. Then the face portion 16 aor the outer radius portion 16 b of the capillary 16 closer to (locatedat the side of) the pad 73 comes into contact with a lateral face of thethird folded portion 88, as shown in FIG. 17. Thus, the third foldedportion 88 is further folded with the face portion 16 a or the outerradius portion 16 b.

As shown in FIGS. 4L and 18, when the capillary 16 is further lowered,the face portion 16 a and the outer radius portion 16 b of the capillary16 closer to (located at the side of) the pad 73 trample the thirdfolded portion 88, so that the upper face of the portion is shapedaccording to the face portion 16 a and the outer radius portion 16 b ofthe capillary 16. At the same time, the end portion of the third foldedportion 88 farther from the pad 73 is bonded to a point 87 a on the lead74 adjacent to the point 86 a in such a manner that a portion of thethird folded portion 88 is overlaid on the bonded portion 85 a of thefirst trampled portion 86 d and the wire loop 85 where bonded to thelead 74 and the first folded portion 86. In this case, the surface withwhich the face portion 16 a of the capillary 16 comes into contactbecomes flat according to the surface of the face portion 16 a of thecapillary. After the third folded portion 88 is bonded to the lead 74,the second trampling bonding step is completed. In this case, the thirdfolded portion 88 can be pressed with the tip end of the capillary 16,and the ultrasonic vibrator 15 can be driven based on a signal from theultrasonic vibrator interface 43 to vibrate the capillary 16.

After the second trampling bonding step, the control unit 30 issues acommand to raise the capillary 16 with the clamper 17 being opened, asindicated by Step S216 in FIG. 13. Based on this command, a signal fromthe movement mechanism interface 44 is output to the bonding head 19.The Z-directional motor installed in the bonding head 19 is then drivento rotate the bonding arm 13 and thereby raise the capillary 16. In thiscase, since the clamper 17 is opened, the wire 81 is fed out of the tipend of the capillary 16.

After the capillary 16 is raised by a predetermined distance, thecontrol unit 30 issues a wire cutoff command, as indicated by Step S217in FIG. 13. Based on this command, a signal from the clamper opening andclosing mechanism interface 41 is output to the clamper opening andclosing mechanism 27. The clamper opening and closing mechanism 27 thencloses the clamper 17. When the capillary 16 is further raised with theclamper 17 being closed, the wire 81 is cut off, as shown in FIGS. 4Mand 19, to be a state where a tail wire 82 extends out of the tip end ofthe capillary 16. Also, at the point 87 a on the lead 74 where thecenter of the capillary 16 is positioned during the second tramplingbonding, there is formed a roundly raised wire cutoff residual 87 d.

FIG. 20 schematically illustrates the locus (trajectory) of the tip endof the capillary 16 through the first trampling bonding step, the thirdfolding step, and the second trampling bonding step described above. Asshown in FIG. 20, in the first trampling bonding step, the tip end ofthe capillary 16 is raised by the height H₁ from the point 86 a wherethe center of the capillary 16 is positioned during the second bondingon the lead 74 to the point “p”, and then moved horizontally by thefirst distance L₁ toward the pad 73, and lowered to the point “r” in thevicinity of (immediately adjacent to) the upper face of the lead 74 toform the first trampled portion 86 d. The height of the point “r” fromthe surface of the lead 74 can be about half the diameter of the wire 81to be bonded. In the third folding step, the tip end of the capillary 16is raised from the point “r” to the height H₂, and then movedhorizontally away from the pad 73, that is, toward the lead 74 by thesecond distance L₂, which is slightly greater than the first distanceL₁. In the second trampling bonding step, the center of the capillary 16is aligned with the point 87 a adjacent to the point 86 a on theopposite side of the pad 73 with respect to the point 86 a, and thenlowered to the point 87 a on the lead 74.

FIG. 21 illustrates the shape of the terminal of the wire loop 85 closerto (located at the side of) the lead 74 formed through theabove-described bonding operation. As shown in FIG. 21, the terminalcloser to (located at the side of) the lead 74 is formed by the firsttrampled portion 86 d and the end portion of the third folded portion 88farther from the pad 73 being pressed and deformed in an overlaid manneron the bonded portion 85 a of the wire loop 85 where bonded to the lead74. The surface of the first trampled portion 86 d and the end portionof the third folded portion 88 farther from the pad 73 is formed in acylindrical recess 87 e following the shape of the tip end of thecapillary 16. The end portion of the recess 87 e farther from the pad 73is the roundly raised wire cutoff residual 87 d. The first trampledportion 86 d extends along the surface of the lead 74 from the wirecutoff residual 87 d toward the pad 73. The third folded portion 88extends in a roll-up manner on the upper face of the first trampledportion 86 d from the wire cutoff residual 87 d toward the pad 73, andthe end portion 87 c thereof closer to (located at the side of) the pad73 is folded to be a round end. The first folded portion 86 is alsointegrated in the roundly raised wire cutoff residual 87 d.

As described heretofore, in this exemplary embodiment, the firsttrampled portion 86 d and the third folded portion 88 are bonded to theterminal of the wire loop 85 closer to (located at the side of) the lead74 in an overlaid manner, whereby the strength of bonding between thewire loop 85 and the lead 74 is increased. Also, a portion of the firsttrampled portion 86 d and the third folded portion 88 is pressed anddeformed with the tip end of the capillary 16 on the bonded portion 85 aof the wire loop 85 where bonded to the lead 74, resulting in a compactshape. At the same time, the shape of the terminal of the wire loop 85can be formed stably. Further, the thickness of the bonded portion wherebonded to the lead 74 can be increased, which allows for preventing heelcrack effectively.

Although the second distance L₂ of the horizontal movement is greaterthan the first distance L₁ of the horizontal movement in the firsttrampling bonding step in the above description of this exemplaryembodiment, the second distance L₂ of the horizontal movement can beequal to or smaller than the first distance L₁ of the horizontalmovement in the first trampling bonding step.

The foregoing description of the exemplary embodiments of the presentinvention has been provided for the purpose of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Obviously, many modificationsand variations will be apparent to practitioners skilled in the art. Theexemplary embodiments were chosen and described in order to best explainthe principles of the invention and its practical applications, therebyenabling others skilled in the art to understand the invention fromvarious embodiments and with the various modifications as are suited tothe particular use contemplated. It is intended that the scope of theinvention be defined by the following claims and their equivalents.

1. A method of manufacturing a semiconductor device having a wire loopto be connected to a first bonding point and a second bonding point witha wire-bonding apparatus having a load sensor for detecting pressingload applied at a tip end of a capillary, the method comprising: a firstbonding step of bonding a wire to a first bonding point by means of acapillary; a second bonding step of, after the first bonding step,bonding the wire to a second bonding point by means of the capillary insuch a manner that the capillary is raised while feeding the wire out ofthe tip end of the capillary and subsequently looped to the secondbonding point along a predetermined trajectory, and then the wire isbonded to the second bonding point, thereby forming a wire loopconnecting to the first bonding point and the second bonding point; afirst folding step of, after the second bonding step, folding the wireon the wire loop by means of the capillary in such a manner that thecapillary is raised while feeding the wire out of the tip end thereofand subsequently moved toward the first bonding point by a firstpredetermined distance, and then the wire fed out of the tip end of thecapillary is brought into contact with the upper face of the wire loop,and the capillary is lowered to the wire loop until the pressing loaddetected with the load sensor becomes equal to a predetermined value,thereby forming the wire fed out of the tip end of the capillary into afirst folded portion having a shape that follows the upper face of thewire loop; a second folding step of, after the first folding step,folding the wire on the first folded portion by means of the capillaryin such a manner that the capillary is raised while further feeding thewire out of the tip end thereof and subsequently moved in a directionopposite to the first bonding point by a second predetermined distance,and then the capillary is lowered, thereby forming the wire further fedout of the tip end of the capillary into a second folded portion havinga shape that follows the upper face on the first folded portion; and athird bonding step of, after the second folding step, bonding the wireby means of the capillary in such a manner that the capillary is loweredto bond the wire to immediately adjacent to a bonded portion where thewire has bonded to the second bonding point, thereby bonding the wirethereto while causing the capillary to crush at least a portion of thefirst and second folded portions located at the second bonding pointside with a face portion of the capillary located at the first bondingpoint side in such a manner as to be overlapped to the wire loop locatedat the second bonding point side.
 2. The method of manufacturing asemiconductor device according to claim 1, wherein the capillary isconfigured to be vibrated ultrasonically, and in the first bonding stepand the second bonding step the capillary is vibrated ultrasonicallyduring bonding operation.
 3. The method of manufacturing a semiconductordevice according to claim 1, further comprising raising the capillarywith the wire in a substantially vertical direction while clamping thewire with a clamper, thereby cutting off the wire.